Proper grounding of Open Theremin V3

So I've decided to take the plunge on an Open Theremin V3. This is more of a fun hobby than anything else. I don't really play any musical instruments.

Anyway, I've managed to build one, and it does play fairly well, but only if I ground myself to the grounding pad of the Open Theremin shield. A grounded AC/DC adapter does not appear to do the trick. I suspect my house isn't properly grounded, but that's a separate conversation.

I know that the Open Theremin site emphasizes the importance of properly grounding the instrument, and I believe I understand why (the player effectively forms one half of a capacitor in the circuit, so he or she needs to be at the same 0V point as the circuit itself, and the grounding pad on the shield is directly connected to circuit ground).

But I have to wonder: how do "real" theremins deal with this issue? If I had bought a commercial theremin, would I not be able to play it properly in my house due to its lack of grounding? What if I wear rubber soles on my shoes? Does that not mean I'm not properly grounded? How exactly does this work with a professional grade theremin?

This is more about satisfying my curiosity than anything else. Thanks for any insight you can give me!

The open theremin need to do grounding through special pads on the circuit Board with the wires going to the water pipes or solid metal objects. You can use a long shielded wires to the amplifier and acoustics.That helps too. Grounding other models of termenvox based on the same principle. Hope is grounded through the socket does not make sense.